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Search: id:A082470
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| A082470 |
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Number of k >= 0 such that k! + prime(n) is prime. |
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+0
2
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| 2, 1, 3, 4, 5, 3, 6, 7, 6, 6, 9, 11, 9, 5, 10, 9, 10, 9, 9, 8, 9, 9, 11, 8, 10, 10, 12, 16, 12, 10, 10, 13, 14, 14, 16, 11, 12, 9, 15, 10, 9, 8, 12, 9, 10, 6, 8, 7, 14, 13, 10, 21, 15, 9, 13, 11, 9, 19, 12, 13, 16, 11, 19, 17, 9, 13
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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k! + p is composite for k >= p since p divides k! for k >= p.
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EXAMPLE
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For n = 4, 3!+7 = 13, 4!+7=31, 5!+7=127 and 6!+7 = 727 are the 4 primes in n!+7
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MAPLE
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for i from 2 to 50 do ctr := 0: for j from 2 to ithprime(i)-1 do if isprime(j!+ithprime(i))=true then ctr := ctr+1 fi od; print(ctr); od;
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PROGRAM
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(PARI) nfactppct(n) = { forprime(p=1, n, c=0; for(x=0, n, y=x!+p; if(isprime(y), c++) ); print1(c", ") ) } - Cino Hilliard (hillcino368(AT)gmail.com), Apr 15 2004
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CROSSREFS
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Sequence in context: A085985 A088267 A117407 this_sequence A101204 A035043 A155963
Adjacent sequences: A082467 A082468 A082469 this_sequence A082471 A082472 A082473
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KEYWORD
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nonn,more
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AUTHOR
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Jeff Burch (gburch(AT)erols.com), Apr 27 2003
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EXTENSIONS
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Edited by Frank Adams-Watters (FrankTAW(AT)Netscape.net), Aug 01 2006
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